Patents relating to golf clubs include U.S. Pat. Nos. 5,419,560; 5,540,437; and 6,702,693, and the references cited or listed therein, and U.S. Patent Application Publication No. US 2006/0183568 A1, Bamber. Patent publications relating to golf putter heads, or attachments thereto, include: U.S. Pat. Nos. 3,319,964; Des. 222,889; Des. 232,371; U.S. Pat. Nos. 3,888,492; 4,034,989; 4,741,535; Des. 324,555; U.S. Pat. No. 5,125,665; Des. 355,944; Des. 381,382; Des. 399,274; D444,832 S; D447,781 S; U.S. Pat. No. 6,488,595 B1; US 2003/0144077 A1; D481,088 S; D481,431 S; U.S. Pat. No. 6,752,723 B2; D500,539 S; D516,655 S; U.S. Pat. No. 7,018,304 B2; D520,584 S; U.S. Pat. No. 7,086,957 B2; and U.S. Patent Application Publication No. US 2006/0094522 A1.
Golf clubs must meet the requirements of the United States Golf Association Rules of Golf (“Rules of Golf”) to be considered “legal” for tournament play. The USGA Rules require in Appendix II, Rule 4a, that:                The club head must be generally plain in shape. All parts must be rigid, structural in nature and functional. It is not practicable to define plain in shape precisely and comprehensively but features which are deemed to be in breach of this requirement and therefore not permitted include:                    (i) holes through the head,            (ii) transparent material added for other than decorative or structural purposes,            (iii) appendages to the main body of the head such as knobs, plates, rods or fins,                         for the purpose of meeting dimensional specifications, for aiming or for any other purpose. Exceptions may be made for putters.         Any furrows in or runners on the sole must not extend into the face.        
The addition of the exception for putters is believed to have been added within the last several years. This Rule, particularly the prohibition on appendages, is believed to be the reason that most golf club heads currently on the market, including putters, do not have portions not used for striking a golf ball that extend significantly laterally outward beyond the striking face of the club head.
An example of the prior thought about this subject is contained in the Background of the Invention of U.S. Pat. No. 6,488,595 B1, which states:                What is needed is a putter that provides a moment of inertia in the range of 12,000 to 28,000 grams per square centimeter (g/cm2). Such a putter would enable a golfer to strike the ball near or at the toe or heel of the putter with little or no loss of accuracy in the shot, i.e., every spot on such a putter would provide a sweet spot.        One possible approach would be to make a putter blade having a very long heel to toe distance measurement, and to attach very heavy weights to its outermost ends. Such a putter, however, would be impractical to use and unattractive to consumers. Moreover, the U.S. Golf Association (USGA) would not approve such a putter for tournament play. The challenge is to provide a putter having a super high moment of inertia that maintains its attractiveness and practicality and that is approved by the USGA for tournament play.        
It is desired to make a putter with improved features, including, in some embodiments, a high moment of inertia, that will conform to the U.S.G.A. Rules of Golf.